import { CompletionItem, CompletionItemKind, Position, CompletionList } from 'vscode-languageserver-types';
import type { TextDocument } from 'vscode-languageserver-textdocument';

import {
  StylusNode,
  buildAst,
  flattenAndFilterAst,
  findNodeAtPosition,
  isFunctionNode,
  isSelectorCallNode,
  isSelectorNode,
  isVariableNode
} from './parser';

import { cssData, LoadedCSSData } from './css-browser-data';
import builtIn from './built-in';
import _ from 'lodash';

function prepareName(name: string): string {
  return name.replace(/\{|\}/g, '').trim();
}

/**
 * Naive check whether currentWord is class or id
 * @param {String} currentWord
 * @return {Boolean}
 */
export function isClassOrId(currentWord: string): boolean {
  return /^[.#&]/.test(currentWord);
}

/**
 * Naive check whether currentWord is at rule
 * @param {String} currentWord
 * @return {Boolean}
 */
export function isAtRule(currentWord: string): boolean {
  return _.startsWith(currentWord, '@');
}

/**
 * Naive check whether currentWord is value for given property
 * @param {Object} data
 * @param {String} currentWord
 * @return {Boolean}
 */
export function isValue(data: LoadedCSSData, currentWord: string): boolean {
  const property = getPropertyName(currentWord);

  return !!property && Boolean(findPropertySchema(data, property));
}

/**
 * Formats property name
 * @param {String} currentWord
 * @return {String}
 */
export function getPropertyName(currentWord: string): string {
  return currentWord.trim().replace(':', ' ').split(' ')[0];
}

/**
 * Search for property in cssSchema
 * @param {Object} data
 * @param {String} property
 * @return {Object}
 */
export function findPropertySchema(data: LoadedCSSData, property: string) {
  return _.find(data.properties, item => item.name === property);
}

/**
 * Handler for variables
 * @param {Object} node
 * @param {String[]} text - text editor content splitted by lines
 * @return {SymbolInformation}
 */
function _variableSymbol(node: StylusNode, text: string[], currentWord: string): CompletionItem {
  const name = node.name;
  const lineno = Number(node.val!.lineno!) - 1;

  const completionItem = CompletionItem.create(name);
  completionItem.detail = text[lineno].trim();
  completionItem.kind = CompletionItemKind.Variable;

  return completionItem;
}

/**
 * Handler for function
 * @param {Object} node
 * @param {String[]} text - text editor content splitted by lines
 * @return {CompletionItem}
 */
function _functionSymbol(node: StylusNode, text: string[]): CompletionItem {
  const name = node.name;

  const completionItem = CompletionItem.create(name);
  completionItem.kind = CompletionItemKind.Function;

  return completionItem;
}

/**
 * Handler for selectors
 * @param {Object} node
 * @param {String[]} text - text editor content splitted by lines
 * @param {String} currentWord
 * @return {CompletionItem}
 */
function _selectorSymbol(node: StylusNode, text: string[], currentWord: string): CompletionItem {
  const firstSegment = node.segments[0];
  const name = firstSegment.string
    ? node.segments!.map(s => s.string).join('')
    : firstSegment.nodes!.map(s => s.name).join('');

  const completionItem = CompletionItem.create(name);
  completionItem.kind = CompletionItemKind.Class;

  return completionItem;
}

/**
 * Handler for selector call symbols
 * @param {Object} node
 * @param {String[]} text - text editor content splitted by lines
 * @return {CompletionItem}
 */
function _selectorCallSymbol(node: StylusNode, text: string[]): CompletionItem {
  const lineno = Number(node.lineno) - 1;
  const name = prepareName(text[lineno]);

  const completionItem = CompletionItem.create(name);
  completionItem.kind = CompletionItemKind.Class;

  return completionItem;
}

function isVisible(useSite: number[] | undefined, defSite: number[] | undefined) {
  if (!useSite || !defSite) {
    return true;
  }
  if (useSite.length < defSite.length) {
    return false;
  }
  for (const [use, def] of _.zip(useSite!, defSite)) {
    if (use && def && use > def) {
      return false;
    }
  }
  return true;
}

/**
 * Returns completion items lists from document symbols
 * @param {String} text
 * @param {String} currentWord
 * @return {CompletionItem}
 */
export function getAllSymbols(text: string, currentWord: string, position: Position): CompletionItem[] {
  const ast = buildAst(text);
  if (!ast) {
    return [];
  }
  const node = findNodeAtPosition(ast, position);
  const scope = node ? node.__scope : undefined;
  const splittedText = text.split('\n');
  const rawSymbols = flattenAndFilterAst(ast).filter(
    item => ['Media', 'Keyframes', 'Atrule', 'Import', 'Require', 'Supports', 'Literal'].indexOf(item.__type) === -1
  );

  return _.compact(
    rawSymbols.map(item => {
      if (!isVisible(scope, item.__scope)) {
        return undefined;
      }
      if (isVariableNode(item)) {
        return _variableSymbol(item, splittedText, currentWord);
      }

      if (isFunctionNode(item)) {
        return _functionSymbol(item, splittedText);
      }

      if (isSelectorNode(item)) {
        return _selectorSymbol(item, splittedText, currentWord);
      }

      if (isSelectorCallNode(item)) {
        return _selectorCallSymbol(item, splittedText);
      }
    })
  );
}

/**
 * Returns at rules list for completion
 * @param {Object} data
 * @param {String} currentWord
 * @return {CompletionItem}
 */
export function getAtRules(data: LoadedCSSData, currentWord: string): CompletionItem[] {
  if (!isAtRule(currentWord)) {
    return [];
  }

  return data.atDirectives.map(property => {
    const completionItem = CompletionItem.create(property.name);

    completionItem.documentation = property.description;
    completionItem.kind = CompletionItemKind.Keyword;

    return completionItem;
  });
}

/**
 * Returns property list for completion
 * @param {Object} data
 * @param {String} currentWord
 * @return {CompletionItem}
 */
export function getProperties(data: LoadedCSSData, currentWord: string, useSeparator: boolean): CompletionItem[] {
  if (isClassOrId(currentWord) || isAtRule(currentWord)) {
    return [];
  }

  return data.properties.map(property => {
    const completionItem = CompletionItem.create(property.name);

    completionItem.insertText = property.name + (useSeparator ? ': ' : ' ');
    completionItem.documentation = property.description;
    completionItem.kind = CompletionItemKind.Property;

    return completionItem;
  });
}

/**
 * Returns values for current property for completion list
 * @param {Object} data
 * @param {String} currentWord
 * @return {CompletionItem}
 */
export function getValues(data: LoadedCSSData, currentWord: string): CompletionItem[] {
  const property = getPropertyName(currentWord);
  const result = findPropertySchema(data, property);
  const values = result && result.values;

  if (!values) {
    return [];
  }

  return values.map(property => {
    const completionItem = CompletionItem.create(property.name);

    completionItem.documentation = property.description;
    completionItem.kind = CompletionItemKind.Value;

    return completionItem;
  });
}

export function provideCompletionItems(document: TextDocument, position: Position): CompletionList {
  const start = document.offsetAt(Position.create(position.line, 0));
  const end = document.offsetAt(position);
  const text = document.getText();
  const currentWord = text.slice(start, end).trim();
  const value = isValue(cssData, currentWord);

  let completions: CompletionItem[] = [];

  if (value) {
    const values = getValues(cssData, currentWord);
    const symbols = getAllSymbols(text, currentWord, position).filter(
      item => item.kind === CompletionItemKind.Variable || item.kind === CompletionItemKind.Function
    );
    completions = completions.concat(values, symbols, builtIn);
  } else {
    const atRules = getAtRules(cssData, currentWord);
    const properties = getProperties(cssData, currentWord, false);
    const symbols = getAllSymbols(text, currentWord, position).filter(
      item => item.kind !== CompletionItemKind.Variable
    );
    completions = completions.concat(properties, atRules, symbols);
  }
  return {
    isIncomplete: false,
    items: completions
  };
}
